1. Technical Field of the Invention
The present invention relates to a telecommunications network and, in particular, to the efficient management of channel resources within a digital mobile communications network.
2. Description of Related Art
The general name of the connection between a particular mobile station traveling within a particular cell area and the base transceiver station (BTS) providing radio coverage for that particular cell area is the "radio interface" or "air interface". Historically, the communications of information across the air interface between a base transceiver station (BTS) and a mobile station has employed, so-called, analog modulation techniques. For example, Frequency Division Multiple Access (FDMA) technology has been widely utilized to assign each mobile station to one of a plurality of the frequency channels associated with the current cell area to communicate with the serving BTS. More recently, however, digital modulation techniques have been used in order to enhance the spectrum efficiency with which the bandwidth allotted to mobile communications is used. As an illustration, the two techniques of time division multiple access (TDMA) and code division multiple access (CDMA) have been utilized to allow communications to proceed between a BTS and a plurality of different mobile stations on a relatively limited amount of radio frequency bandwidth. The Global System for Mobile (GSM) communications system, for example, utilizes the TDMA concept with the allocation of one TDMA frame per carrier frequency channel to communicate between a mobile station and a BTS. Each frame is further subdivided into eight time-slots (TS). Each time-slot of a TDMA frame on a single frequency channel is referred to as a physical channel. Accordingly, there are eight physical channels per carrier in the GSM system. Each physical channel of the GSM system can be compared with one single channel in an FDMA-system, where every user is connected to the system via one of the associated frequencies.
The implementation of TDMA technology requires that a great quantity and variety of information must be transmitted between the serving BTS and the mobile station over the limited physical channels. For example, control data, service request data, actual traffic data, supplementary data, etc., have to be communicated over the physical channels. As a result, in order to distinguish one type of data from another, different logical channels have been named and mapped (assigned) on to the available physical channels. For example, actual speech is sent on the logical channel named "traffic channel (TCH)" occupying one or more physical channels. Paging of a called party mobile station is performed over the logical "paging channel (PCH)" while synchronization of a mobile station with a serving BTS is performed over the logical "synchronization channel (SCH)" which occupies one of the physical channels. Accordingly, depending on the type of information being transmitted, different logical channels are utilized. Needless to say, if more physical channels are assigned to a particular logical channel, a lesser number of physical channels are available for the rest of the logical channels.
Because of the limited physical channel resources, mobile service providers are often faced with channel resource management and dimensioning problems. One such problem includes effectively managing Stand-alone Dedicated Control Channels (SDCCH) within a serving mobile network. Because of the fact that congestion in SDCCH logical channels results in lost calls and unsuccessful call setups, the efficient management of SDCCH logical channels is critical for providing reliable mobile service to mobile stations traveling within the serving coverage area.
SDCCH logical channels are not only utilized for setting up call connections, but also for performing location updates for traveling mobile stations and for communicating packet messages containing text or graphic data between the serving mobile network and associated mobile stations. Conventionally, all of the above mentioned functionalities are provided the same priority and allowed equal access to available SDCCH channel resources. As a result, all of the available SDCCH channel resources could be occupied by Short Message Service (SMS) or Unstructured Supplementary Service Data (USSD) messages transporting text messages and could, as a result, prevent speech connections from being established between mobile stations and a serving mobile network. However, even though the support of all of the above mentioned functionalities is important for providing reliable and comprehensive mobile service to associated mobile stations, establishing call connections is by far the most important role performed by the mobile network.
Accordingly, there is a need for a mechanism to prioritize mobile services within a serving mobile network to better utilize available SDCCH logical channels.